A power conversion device that includes a DC circuit unit includes a filter capacitor intended to smooth a DC voltage for stably controlling the device and to suppress a generated harmonic current. Generally, a film capacitor is used as this filter capacitor. This film capacitor generally contains flammable mineral oil or vegetable oil inside of a case. Because this oil has a possibility of ignition and the film is also flammable, it is necessary to provide a protection mechanism such as a fuse so as to prevent the ignition.
A conventional power conversion device is intended to improve safety and to make the device downsized and lightweight by adopting a filter capacitor provided with segment fuse mechanisms or the like. If a short circuit occurs between films due to an external factor such as an overvoltage or an internal factor such as a defect in the film itself, one of these segment fuse mechanisms is operated by a flowing short-circuit current, only a segment to which the short circuit occurs is separated from the other segments. The capacitor maintains to function by the remaining faultless segments and functions to prevent the rupture of a capacitor case and ignition (for example, Patent Literature 1 mentioned below).
Furthermore, Patent Literature 2 mentioned below proposes a protection device that includes detection means for detecting a short circuit that occurs in a capacitor provided in a DC main circuit of a power converter as means for preventing explosion resulting from a short circuit of the capacitor, that turns on a switch connected in parallel to this capacitor, and that prevents a short-circuit current from flowing to the fault capacitor.